GEOLOGY OF OLYMPIC NATIONAL PARK:
PART I OLYMPIC GEOLOGY

Fig. 11.
The ribbon of time. For details of the Tertiary Period and the geologic
timescale in general, click
here.

Rocks and Time

Contemplation
of earth history is always hindered by the mind-boggling dimensions
of geologic time. We can talk about a million years or even a billion
years, but we can hardly imagine the countless small events that fill
such expanses of time. And it is just such small events the settling
of a sand grain to the ocean bottom, the tumbling of an unsteady pebble
into a creek, the death of a small snail†that add up to geologic change.
If we travel down the Elwha River from Lake Mills to Lake Aldwell, we
will have traversed in about 5 miles a section of rock†basalt, shale,
and sandstone representing about 10 to 15 million years of accumulation.
If we were to walk through time at this same rate, a few paces more
would encompass all of mankind's recorded history, and a slight shuffle
of an inch or so would take in one person's lifetime (fig. 11). To pace
out the whole of the earth's history since its beginning about 4.5 billion
years ago, we would have to hike about 1,500 miles.

Fig. 12. Seastacks of coarse coglomerate and breccia make up The Point of the Arches. These rocks, full of pieces of the old gabbro, overlie it.

The Oldest Rocks

Geologists
are wont to ask upon what all the sedimentary and volcanic rocks of
the Olympics were deposited, a question not unlike that of the Greeks
who wondered where Atlas stood as he held up the earth. The answer is
not entirely clear, but most of the Olympic rocks may have been laid
down directly on basaltic crust under the Pacific Ocean. Some rocks,
however, were deposited on the eroded surface of older igneous and sedimentary
rocks †perhaps a submerged piece of the North American continent of
70 million years ago. Just south of Point of Arches, modern sea cliffs
and sea stacks of old gabbro, basalt, and sandstone may represent this
piece of continent. Some of the old rocks at Point of the Arches (see
the geologic map) are at
least 144 million years old, that is, at least 80 million years older
than the oldest rocks in the Olympic Mountains (fig. 11).

Cliffs
at Point of Arches, reached via Shi Shi beach on the Makah Indian Reservation,
reveal Eocene conglomerates and breccias filled with large boulders
eroded from the old continent (fig. 12). The intrepid explorer can reach
the old gabbro a rock of white (feldspar) and black (hornblende) spots†by
scrambling along the cliffs south of the point at low tide.

To approach
the gabbro from the south, drive to the beach north of the Ozette River
and hike north at very low tide.